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SubjectRe: [PATCH 5/6] x86,fpu: also check fpu_lazy_restore when use_eager_fpu
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On 02/02/2015 01:55 PM, Oleg Nesterov wrote:
> On 02/02, riel@redhat.com wrote:
>>
>> From: Rik van Riel <riel@redhat.com>
>>
>> With Oleg's patch "x86, fpu: don't abuse FPU in kernel threads
>> if use_eager_fpu()", kernel threads no longer have an FPU state
>> even on systems with use_eager_fpu()
>>
>> That in turn means that a task may still have its FPU state
>> loaded in the FPU registers, if the task only got interrupted by
>> kernel threads from when it went to sleep, to when it woke up
>> again.
>>
>> In that case, there is no need to restore the FPU state for this
>> task, since it is still in the registers.
>>
>> The kernel can simply use the same logic to determine this as is
>> used for !use_eager_fpu() systems.
>
> Yes, agreed, I was going to do this too.
>
> And in fact this change make sense even without "don't abuse FPU in
> kernel threads", I think.
>
> But in theory it depends on another change, "__kernel_fpu_begin()
> should clear fpu_owner_task even if use_eager_fpu()".
>
> And that series was ignored ;)
>
> I think this patch is fine.

Ingo,

does the FPU code have a sub-maintainer, or should all the
FPU patches go straight through you?

Would it be better for you if FPU patches came through a git
tree you could just pull?

- --
All rights reversed
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